Syringe

ABSTRACT

A cartridge for use in a hypodermic syringe characterized by an aspirating piston comprising a resilient body portion taking the general form of a cylinder; two voids extending in opposite directions within such body portion; and, separating the two voids from each other, a transverse web provided with oppositely directed protuberances.

United States Patent Inventor Myron F. Levenson 2974 Montgomery Road, Shaker Heights, Ohio 44122 Appl. N9. 794,867 Filed Jan. 29, 1969 Patented Nov. 9, 1971 SYRINGE 3 Claims, 10 Drawing Figs. (1.8. CI 128/218 P, 1 28/272 Int. Cl ..'.A61m05/22 Field of Search 128/218, 218 P, 218 PA, 218.1, 219, 220, 272

Primary ExaminerSamuel Koren Assistant Examiner-J. S. Reich I Attorney-Bosworth, Sessions, Herrstrom & Cain ABSTRACT: A cartridge for use in a hypodermic syringe characterized by an aspirating piston comprising a resilient body portion taking the general form ofa cylinder; two voids extending in opposite directions within such body portion; and, separating the two voids from each other, a transverse web provided with oppositely directed protuberances.

svxmca II. PRIOR ART This invention relates to an ampul or cartridge provided with an aspirating piston for intended use in a hypodermic syringe that may otherwise be largely or entirely conventional.

In its simplest form, the common hypodermic syringe has a piston that can be pulled rearwardly (usually by means of a retractible plunger) from a forward position with a view to producing liquid aspiration into the interior of the syringe. Even though not expressly designed as aspirating syringes, some types of cartridge-loaded syringes can be used in similar fashion for aspirating purposes. An example can be seen when, after introduction of the needle into muscle tissue, the plunger is first urged forward to a limited extent and then withdrawn slowly to determine whether the needle has penetrated a blood vessel.

It is commonly acknowledged that, unless it is impracticable so to do, this practice should be followed as a matter of routine whenever muscle injection is contemplated.

Unfortunately, limited aspiration for these purposes has to be ruled out for some types of hypodermic syringes; e.g., those illustrated in expired U.S. Pats. Nos. 2,5 26,365 and 2,554,744 to Jorgensen, mainly because of their relatively insensitive response to attempted aspiration. More than one factor may be involved in such cases, but in certain of them the insufficiency may be attributed to the fact that hollow pistons of kinds known to the prior art distort to an undesirable degree under the pressure of a plunger. This is believed to be attributable in part to the fact that in such cases geometrical symmetry has been absent; at any rate, it is widely recognized that where a hollow piston has a basically unbalanced configuration, the desired degree of sensitivity is seldom achieved.

By contrast, the present invention provides a syringe cartridge equipped with a hollow piston characterized by end-forend symmetry and, as it happens, a relatively high degree of sensitivity.

Ill. BRIEF DESCRIPTION OF DRAWINGS Other objects, advantages and features of the invention will be apparent from the specification which follows and from the accompanying drawings, in which:

FIGS. 1 and 6 are side elevations of two syringes within the purview being shown in section;

FIGS. 2 to 4 are enlarged sections showing the details of the piston of FIG. 1 and illustrating the physical changes which occur in it incident to use of the syringe;

FIGS. 7 to 9 are similar sections showing the details of the piston of FIG. 6 and illustrating the changes which occur in it incident to use of the syringe.

FIGS. 5 and are in the main much enlarged longitudinal sections through the two pistons.

generally similar of the invention, parts of each IV. PREFERRED EMBODIMENTS OF THE INVENTION In FIG. 1 of the drawings, the syringe indicated at 1 includes certain conventional elements such as a metal, glass or plastic outer shell 2, a metal needle fitting 3, and a double-ended metal needle 4, both of the latter being at the forward or leading end of the shell. At its opposite or trailing end, the syringe carries a conventional plunger assembly comprising a thumb rest 5, a plunger rod 6, and an enlarged head 7. Plunger rod 6 passes through a metal fitting 8 by which it is supported in a manner afi'ording easy sliding movement longitudinally of the syringe. Outwardly thereof, threaded onto the adjacent end of shell 2, is a metal cap 9 equipped as desired with one or more finger rests 10 of any desired shape.

Syringe 1 may in some instances come complete with cartridge 11, but generally the latter will constitute an independent article of commerce. It consists of a cylindrical portion 12 at one end of which is a stout plug 13 provided as shown with a shoulder 14 accommodating in essentially fluidtight fashion the proximate end of cylindrical portion 12. At the opposite end of cylindrical portion 12 is a hollow piston 15.

Cylindrical portion 12, while not necessarily rigid, should at least be rather stiff. End plug 13 should ordinarily be of a softer material, soft enough to permit needle 4 to pass through it without undue difiiculty. Piston 15 should be sufficiently resilient to permit it to form a liquidtight seal where it engages cylindrical portion l2. The forward end (but if desired both ends) of the cartridge will ordinarily be sealed by a cap of metal foil. Frequently the cap will be left in place when the cartridge is inserted in outer shell 2, but for reasons of convenience FIGS. 2, 3 and 4 omit any showing of it.

Piston 15 has a hollow body portion 16 of cylindrical shape, circular grooves 17 in its exterior surface, and a transversely extending internal web 18 located midway between the opposite ends of the body portion. Formed integrally with and projecting in opposite directions from web 18 are thrustreceiving protuberances 19, 22 of the nature of elongated lobes. Lobe 19 is surrounded by a cylindrical void 20; lobe 22, by a like void 21. The overall length a of the structure as a whole (i.e., web 18 and protuberances 19, 22) exceeds that of the piston by nearly half. See FIG. 5.

When, as suggested by FIGS. 1 to 3, the plunger assembly is urged from left to right by light pressure on thumb rest 5, plunger head 7 first moves into engagement with the near end of the thrust-receiving piston structure. After contact with lobe 19 has been established, further light pressure on the plunger assembly results in displacement of the thrust-receiving structure within the confines of piston body 16, thereby producing the type of web distortion illustrated at 18' (FIG. 3) without moving the piston itself. In the meanwhile, a very small amount of the liquid in the cartridge cavity leaves double-ended needle 4 in the manner indicated by the arrows.

If, as will usually be the case, the user is desirous of ascertaining whether the needle has entered a blood vessel, he will withdraw his thumb from thumb rest 5 as soon as the indicated degree of displacement of the thrust-receiving structure has come about. If it appears to be desirable, he may then pull the plunger assembly to the left, seen as in FIG. 4. Usually, however, it will not be necessary to do so, for as a rule, when web 18 is deflected to the degree indicated at 18 in FIG. 3, it tends to urge plunger head 7 in a direction opposite to the original direction ofmovement; i.e., to the left as seen in FIG. 4.

In either case, return of the thrust-receiving structure to the symmetrical configuration illustrated in FIG. 2 gives rise to the aspirating action indicated in FIG. 4 by the group of arrows at the inboard end of needle 4. At this stage and in this way, the user can tell, from the color of the liquid drawn back into the cartridge, whether, as a consequence of having penetrated a blood vessel, he should find a new site at which to inject the liquid contents of cartridge 11.

In the form of the invention shown in FIGS. 6 to 10, like reference characters (e.g. reference characters I to 14) refer to parts in the two embodiments of the invention that do not differ materially from each other. In many respects, piston 25 is analogous to piston 15, but it departs therefrom in that piston body 26, which is grooved as at 27, takes the general form of a hollow cylinder characterized by a rather simple transversely extending web 28. The latter is centrally located between the two ends of the piston body.

Thus web 28 divides the hollow within piston body 26 into two oppositely extending cylindrical voids 29, 30. Each of the latter is centered in relation to the exterior surface of the piston body. It follows that the longitudinal axes of voids 29, 30, considered separately, are continuations of each other; also, that the overall axis of the two voids coincides with the longitudinal axis of piston 25.

Web 28 is not planar but characterized by shallow protuberances 28a and 28b (FIG. 10). If desired, the latter may be regarded as vestigial lobes analogous to, but of considerably lesser altitude than, the lobes 19, 22 of piston body 16. Like the latter, protuberances 28a and 28b are formed integrally with the rest of the web. They comprise thrust-receiving means designed to accept the thrust of a stud 32 projecting from forward face 31 of piston head 7. In general, protuberances 28a and 28b impart to web 28 the appearance of a thickened portion so disposed as to provide geometrical symmetry. See FIG. 10.

When plunger head 7 is moved from the position shown in FIG. 7 to that shown in FIG. 8, stud 32 deflects web 28, producing the distortion indicated at 28' in FIG. 8. This results in displacement through needle 4 of some of the liquid between web 28 and end plug l3. The movement is indicated by the arrows at the ends of needle 4 (FIG. 8). Upon return movement of the plunger assembly. web 28 resumes its original position, thus allowing liquid to flow back into the space between end plug 13 and web 28. If, at this stage the incoming fluid reveals a discoloration, the user should seek a new site for the injection.

Thus in each of these two fonns, the invention provides an aspirating piston characterized by geometrical symmetry about a transverse plane passing through web 18 or web 28, as the case may bev In the form of the invention shown in FIGS. I to 5, the overall length of piston 15 is considerably less than the overall length of protuberances I9, 22, taken with intervening web 18. In the fonn of the piston shown in FIGS. 6 to 10, on the other hand, the distance between posterior surface 28a and anterior surface 28b of web 28 is but a fraction of the length of piston 28.

Whether the protuberances be elongated as in FIG. or vestigial as in FIG. 10, the action is the same in the sense that in both cases the protuberances act as thrust-receiving means, reacting in one case to pressure applied by the plunger head and in the other to the pressure applied by a pilot projecting forwardly from it. In both cases, transmittal of the force to the web leads to its dissemination between the ends of the piston with attendant improvement of overall sensitivity of the syringe. Unilateral distortion at the trailing of the piston is avoided, thereby eliminating factors that are believed to impair sensitivity.

It is intended that the patent shall cover any and all features of patentable novelty residing in the invention.

I claim:

1. In a cartridge for a hypodermic syringe of the type having a barrel adapted to contain a fluid and a plunger adapted for reciprocation within the barrel: an aspirating piston for engagement by the plunger and effective to increase the sensitivity of the syringe to the aspirating action of said piston, said piston comprising a hollow cylindrical body portion, a distensible web joined to and extending transversely of the hollow cylinder, and a relatively large protuberance extending substantially equally from each side of the web beyond the 0pposite ends of the piston and axially of the hollow cylinder, the trailing protuberance being adapted to be engaged by the plunger and axially thrust inwardly to distend the transverse web, the leading protuberance being thereby responsively thrust from the opposite end of the piston into the body of such fluid, the volume of the fluid displaced by said relatively large intruding protuberance increasing the pressure of the fluid in said barrel and thereby the sensitivity of the syringe to such aspirating action of the piston.

2. The cartridge of claim 1 in which the protuberances substantially fill the hollow portion of said cylinder.

3. The cartridge of claim I in which said web is sufficiently distensible that said protuberances maybe axially displaced to effect aspiration without moving said piston relatively to the barrel, thereby avoiding expressing fluid unnecessarily from said syringe.

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1. In a cartridge for a hypodermic syringe of the type having a barrel adapted to contain a fluid and a plunger adapted for reciprocation within the barrel: an aspirating piston for engagement by the plunger and effective to increase the sensitivity of the syringe to the aspirating action of said piston, said piston comprising a hollow cylindrical body portion, a distensible web joined to and extending transversely of the hollow cylinder, and a relatively large protuberance extending suBstantially equally from each side of the web beyond the opposite ends of the piston and axially of the hollow cylinder, the trailing protuberance being adapted to be engaged by the plunger and axially thrust inwardly to distend the transverse web, the leading protuberance being thereby responsively thrust from the opposite end of the piston into the body of such fluid, the volume of the fluid displaced by said relatively large intruding protuberance increasing the pressure of the fluid in said barrel and thereby the sensitivity of the syringe to such aspirating action of the piston.
 2. The cartridge of claim 1 in which the protuberances substantially fill the hollow portion of said cylinder.
 3. The cartridge of claim 1 in which said web is sufficiently distensible that said protuberances may be axially displaced to effect aspiration without moving said piston relatively to the barrel, thereby avoiding expressing fluid unnecessarily from said syringe. 